1. Field of the Invention
The present invention relates to a throttle valve control device of an internal combustion engine. More particularly, the present invention relates to an electronically-controlled throttle valve control device of an internal combustion engine.
2. Description of Related Art
An electronically-controlled throttle valve control device of an internal combustion engine is taught, for example, by Japanese Laid-Open Patent Publication No. 2004-301118.
As shown in FIGS. 9 and 10, this electronically-controlled throttle valve control device includes a throttle body 114, a throttle valve 104, a gear reducer 126 and a coil spring 100. The throttle body 114 has an air intake passage 114a that is formed therein. The throttle valve 104 is connected to a throttle shaft 105 and is received in the air intake passage 114a of the throttle body 114 so as to close and open the air intake passage 114a. The throttle shaft 105 is rotatably attached to the throttle body 114.
The gear reducer 126 is arranged and constructed to transfer a rotative force of a drive motor 110 (an actuator) to the throttle valve 104. In particular, the gear reducer 126 is constructed of a valve gear 111, a pinion gear 113 and an intermediate reduction gear 112. The valve gear 111 is connected to the throttle shaft 105, so as to rotate the throttle valve 104 in a fully opening direction and a fully closing direction. The pinion gear 113 is connected to an output shaft of the drive motor 110. The intermediate reduction gear 112 is meshed with the valve gear 111 and the pinion gear 113. The coil spring 100 is constructed of a single torsion coil spring. One end portion 100a of the coil spring 100 engages an engagement portion 121 that is positioned in a side of the throttle body 114. Conversely, the other end portion 107 of the coil spring 100 engages an engagement portion 122 formed in an opener member 106 attached to the valve gear 111.
Further, the valve gear 111 has a spring guide 108 that is capable of supporting a valve gear-side coiled portion of the coil spring 100 from inside. Conversely, the throttle body 114 has a spring guide 125 that is capable of supporting a throttle body-side coiled portion of the coil spring 100 from inside. Further, the opener member 106 of the valve gear 111 is biased by the coil spring 100 in the fully opening direction or the fully closing direction of the throttle valve 104.
The coil spring 100 has a first spring portion 101 having a coiled portion, a second spring portion 102 having a coiled portion, and a U-shaped hook portion 103. The first spring portion 101 biases the opener member 106 of the valve gear 111 in a direction in which the throttle valve 104 can be closed from a position opened beyond a middle position toward the middle position. To the contrary, the second spring portion 102 biases the opener member 106 of the valve gear 111 in a direction in which the throttle valve 104 can be opened from a position closed beyond the middle position toward the middle position. Further, the first spring portion 101 has a spring force greater than the spring force of the second spring portion 102. The U-shaped hook portion 103 is formed by bending a portion of the coil spring 100 (a boundary portion of the first and second spring portions 101 and 102) to a substantially U-shape. As a result, the coil spring 100 has a coiled portion (an intermediate coiled portion) 103a that is positioned adjacent to or continuous with the U-shaped hook portion 103 and is positioned between the coiled portions of the first spring portion 101 and the second spring portion 102.
Further, the U-shaped hook portion 103 may function as a winding direction changeover portion in which winding directions of the first spring portion 101 and the second spring portion 102 are changed over. That is, the first spring portion 101 has a winding direction different from the second spring portion 102. Further, the U-shaped hook portion 103 engages an engagement portion 124 formed in the opener member 106 by a spring force of the second spring portion 102. Further, the U-shaped hook portion 103 is capable of engaging an intermediate stopper member 115 disposed in a throttle body-side when the throttle valve 104 is closed from the middle position toward the fully closed position thereof.
Therefore, if electric power supplied to the drive motor 110 is stopped or lost, the throttle valve 104 can be maintained in the middle portion due to a difference between the spring force of the first spring portion 101 and the spring force of the second spring portion 102, so that the internal combustion engine can be prevented from being suddenly stopped. Thus, a vehicle can be moved to a safe place.
However, in the electronically-controlled throttle valve control device thus constructed, the intermediate coiled portion 103a of the coil spring 100 that is positioned adjacent to the U-shaped hook portion 103 is formed to be coaxial with a central axis of each of the coiled portions of the first and second spring portions 101 and 102 (i.e., a central axis of remaining coiled portions of the coil spring 100). Therefore, in a condition in which the coil spring 100 is attached to the valve gear 111, due to a reactive force of the second spring portion 102, the intermediate coiled portion 103a of the coil spring 100 can be strongly pressed against the spring guide 108 of the valve gear 111 in a direction shown by an arrow Y in FIG. 10.
When the throttle valve 104 is closed and opened between the middle position and the fully closed position, the valve gear 111 is rotated while the U-shaped hook portion 103 of the coil spring 100 engages or contacts the intermediate stopper member 115 of the throttle body 114. As a result, the spring guide 108 of the valve gear 111 can move or rotate relative to the intermediate coiled portion 103a of the coil spring 100. At this time, because the intermediate coiled portion 103a of the coil spring 100 is pressed against the spring guide 108 of the valve gear 111 due to the reactive force of the second spring portion 102, a large sliding frictional force can be generated between the intermediate coiled portion 103a and the spring guide 108. As a result, a large rotational load can be applied to the drive motor 110. Also, a noise can be generated between the intermediate coiled portion 103a and the spring guide 108.